Culpable Homicide not an Offence, But a Defence?

Yaar, maine toh kai coaching notes dekhe hain jo bolte hain ki Culpable Homicide (Section 299 IPC) ek offence hai, lekin sach to ye hai ki ismein wapas court ki madad karna hai. Ye Culpable Homicide wala concept, jise aap section 300 IPC ke madhyam se pata karenge, ismein wapas wala dharna hai. Section 299 bolta hai ki jab koi aadamiyaan ki zindagi ko marenge toh woh Culpable Homicide ke liye accountable hain, lekin section 300 ka rule hai ki woh aisey case jahaan ek intentional murder ho.